Off season liquid chiller control device



Filed Jan. 9, 1957 D. B. GARDNER 2,979,915

OEE SEASON LIQUID CHILLER CONTROL DEVICE 2 Sheets-Sheet 1 mgm/@Wr April18, 1961 D. B. GARDNER 2,979,915

oFF sEAsoN LIQUID CHILLER coNIRoL DEVICE Filed Jan. 9, 1957 2sheets-sheet 2 IN V EN TOR.

b/ma 5. @anime/7 OFF SEASON LIQUID CHILLER CONTROL DEVICE Filed Jan. 9,1957, Ser. No. 633,328

"4 Claims. (Cl. 62--132) My invention relates to yan off season liquidchiller control device and method, and more particularly, to a methodand device for preventing the accumulation of liquid refrigerant in theevaporator tubes o-f the chiller during olf season periods, or periodsof prolonged shutdown.

A major problem confronting the owner or operator of, for instance,large capacity liquid chillers, is created during periods when operationof the chilling equipment is not required, such as during the wintermonths when the apparatus is not put into operation over a period ofmany weeks.

It is generally known in the art that most valves in a refrigerationsystem allow -at least a small amount of leakage, whether they aremanually or automatically operated. When a refrigeration system stops,conventionally a valve in the refrigerant liquid line is closed, whichcauses the system to concentrate the liquid refrigerant in thecondenser. iIt is known that when this happens, the refrigerant tends toleak by this valve in either liquid or gaseous form and collects inliquid form in the coolest portion of the system, which ordinarily isthe evaporator, conventionally located within the liquid chiller.

Short intervals of non-operation `do not effect the efficiency of thesystem nor endanger the compresson,

nited States Patent "O but during long periods of shutdown, there issome v l danger that relatively large quantities of liquid refrigerantwill accumulate in the evaporator, especially if special efforts havenot been taken to 'insure that the refrigerant is isolated in thecondenser.V If this accumulation occurs,

when the compressor is again started, it is possible to move, or slug,the accumulated liquid refrigerant from the evaporator into thecompressor with consequent dam, age to the compressor. Y The principalVobject of my invention is to providena device and method for insuringthat refrigerant does not accumulate in the evaporator tubing, of liquidchillers and the like. Y

Another object of the invention is to provide a device and method forprotecting the refrigeration systems of liquid chillers againstaccumulation of liquid refrigerant in the evaporator therefor whichpermits automatic operation of theV refrigeration systemthoughout theentire year.

A further object of the invention 'is to provide a-device `forcontrolling the temperature of the evaporator during shutdown periods toprevent accumulation `of liquid refrigerant therein. v Yet a furtherobject of the invention is to provide a liquid chiller temperaturecontrol which is susceptible of a wide variety of embodiments, which isof general application to apparatus of this character', which is eicientin operation, and which is of the utmost simplicity of design therebymaking for inexpensive installation and manufacturing cost.

vln accordance with the principles of my invention, the

Patented Apr. 187, 1961 liquid to be chilled that remains in the liquidchiller upon shutdown is heated sufficiently to raise and maintain thetemperature of the evaporator above that of the condenser. I prefertoheat this remaining liquid to approximately 10 degrees Fahrenheitabove room temperature (assuming 68 degrees Fahrenheit to be roomtemperature) and maintain it at this temperature during the period ofshutdown. This insures that the refrigerant will be driven from theevaporator through the system to the condenser where it collects.

Other objects, uses, and advantages will be obvious or become -apparentfrom a consideration of the following description and the accompanyingdrawings. A In the drawings: y

Figure 1 is a diagrammatic view of a chiller for liquids such as watertogether with the refrigeration system therefor, illustrating myinvention applied to the chiller;

Figure 2 is a diagrammatic cross-sectional view along line 2 2 of Figurel;

Figure 3 is a diagrammatic illustration of a preferred form of switchfor controlling the operation of the chiller refrigeration system andthe temperature control device shown in Figures 1 and 2;

Figure 4 is a diagrammatic perspective view, partially in section andwith parts broken away, illustrating some of the structural features ofthe chil-ler; and

Figure 5 is a diagrammatic view illustrating a modified form of theinvention and the system for operating same.

Reference numeral 10 of Figure l generally indicates a liquid chillerand reference numeral `12 generally indicates a diagrammaticallyillustrated refrigeration system therefor. The chiller 10 may be of thetype manufactured by Bell & Gossett Company of Morton Grove, Illinois,and generally comprises a substantially cylindrical hollow' body or tank14 to which inlet conduit 16 and outlet conduit 18 are connected forbringing the liquid to be chilled, such as water, to the chiller andconveying same therefrom to the point of use.

The chiller 10 includes a plurality of refrigerant tubes 20 (see Figure4) mounted therein in any suitable manner through which thecooling uid,such as Freon 12 Ipasses in performing its function of cooling theliquid to be chilled. Suitable supporting baflles (not shown) areordinarily provided. The chiller 10 is conventionally provided with arefrigerant inlet conduit 22, a refrigerant outlet conduit 24 kand arefrigerant charging valve 26 which is only diagrammaticallyillustrated. The conduits 22 and 24 are connected into the refrigerationsystem 12 which, as indicated in Figure l, may include a suitable heatexchanger 28, a compressor 30, and a condenser 32. The conduit 24communicates with the compressor 30 through appropriate piping 34 whichin turn communi- 22 through kappropriate piping 38 that passesthrough vheat exchanger 28 and has mounted therein a strainer 40, a shutoff valve42, a solenoid valve 44, and a thermostatic expansion valve 46. Thechiller 10 may be surrounded by appropriate insulation 48 in an amountdetermined by the operating conditions of the particular installation.

The chiller and the refrigeration therefor illustrated may be composedof conventional elements and devices in a manner well known inthe artand the diagrammatic illustration of Figure 1 is provided forillustrative ypur'- poses only.

The chiller and its refrigeration system illustrated in Figure 1 ismodified in accordance with the principles of my invention to provide aheater or heat exchange device that will heat up the water or otherliquid remaining in the chiller during the shutdown period to thedesired temperature. One form of appropriate heater or heat exchangedevice is generally indicated by reference numeral 50 of Figures l and2.

The device 50 comprises an adapter element 52 iixed to the wall 54 ofthe chiller in any appropriate manner, as by welding, in which is screwthreadedly mounted a fitting 56. A control box 58 is fixed to the outerend of fitting 56 in any suitable manner;v Fixed to the inner end of theiitting 56 is a metallic container 60 which forms a well for electricheater element 62 that is received therein. The container 60' may beformed from a heat conducting substance such as copper and may be fixedto the iitting 56 in any suitable manner, as by brazing. The heater 62may comprise a 75 or 100 watt, 220 volt single phase cartridge heaterprovided with appropriate wiring 64 that extendsY into the control box58. The control box 5S may be arranged in any conventional or suitablemanner to provide electric current for the heater 62, though thevarrangement illustrated in Figure 3 is preferred. Preferably, a doublethrow switch 7i) is mounted between the terminals 71 yof the wiring 64and the terminals 73 of the wiring 72 that controls the refrigerationcompressor and controls, the switch 70 being connected to power lines 74that are in turn connected to a source of electrical energy.

The outlet piping 18 of the chiller may be formed with the S curveindicated in Figurel to act as a convection ow check when heater 62 isturned on.

In operation, when the switch 70 is operated to shut oft the chiller 10,it is moved to connect the heater device 62 to the source of electricalenergy. Preferably, the heater device 62 is designed to yheat the wateror other liquid remaining in the chiller to approximately 10 degreesFahrenheit above room temperature (which ordinarily approximates 68degrees Fahrenheit) and maintain this liquid at that temperaturethroughout the period of shutdown.

By heating the liquid to be chilled` that remains in the chiller aftershutdown has occurred, the accumulation of liquid refrigerant within theevaporator tubes of the chiller is prevented. The temperatures specifiedare preferred, though the arrangement of the refrigeration systemillustrated are exemplary only. The essential factor is that thetemperature of the evaporator tubing should be maintained at atemperature above that of the condenser. If this is done,.refrigerant onthe low pressure side of the system will move through the system to thecondenser an-d remain there during the period of idleness. It is helpfulto position the chiller at the lowest point in the system with regard toelevation, with the condenser positioned above the chiller and thecompressor positioned above the condenser. However, these relativelocations may be altered without adversely affecting the beneficialresults provided by my invention.

The principal reason Why my invention eiectively prevents theaccumulation of liquid refrigerant in the chiller evaporator tubes isthat the refrigerant tends to move to and accumulate in the coolest partof the refrigeration system. Heretofore, the coolest part has been theevaporator tubes. By heating these evaporator tubes so that thetemperature of the evaporator will be above that of the condenser, therefrigerant will naturally seek the condenser, which is where therefrigerant should be during shutdown periods.

Figure 5 diagrammatically illustrates the modied form of heater appliedto the chiller 10a which is similar in structure to the chiller 1i).Reference numeral 65 generally indicates a heated fluid type of heatexchanger which includes diagrammatically illustrated tubing 67 thatextends into the interior of the chiller lila in a manner similar tothat of the device 5t). The heater 65 as illustrated is incorporated ina gravity operated circuit for supplying same with hot water from aconventional boiler 69, the main purpose of which is to heat radiators66 of a building or other structure as well as a domestic faucet water.Water is supplied to the boiler through suitable piping 75 and is heatedin a conventional manner by a suitable burner operated by controls thatmaintain a constant boiler water temperature, Whenever thermostaticcontrols call for heat, a circulating pump 77 is operated to pump heatedwater through piping 79 to the radiator or radiators 66. Water from theradiators 66 (only one of which is shown) returns to the boiler throughappropriate piping 76, including a ow control valve 78 and communicatingwith a conventional expansion tank 80 through a pipe 82. Domestic hotwater is drawn from the boiler through appropriate piping 84 and coldwater enters the boiler through piping 86. Drain piping 88 may also beprovided which includes a suitable control valve 90.

The heater 65 is supplied with hot water through appropriate piping 92in which is interposed a suitable form of gate valve 94 and anappropriate vent valve 96. The water passing from heater 65 flows to thedrain piping 88 through appropriate piping 98 and when valve is closedit is drawn by pump 77 back to the piping 79. Gate valve 94 is adjustedto permit a liquid flow that will heat the liquid remaining in thechiller to approximately 10 degrees Fahrenheit above room temperature.

It will be appreciated that the system diagrammatically illustrated inFigure 5 provides results similar to those of the system of Figures land 2 in heating the chiller evaporator to a temperature above that of arefrigeiration system condenser. Of course, a steam heat exchangersimilar to the hot water heat exchanger 65 may be employed in a similarsystem connected with a steam boiler. In either type of heated fluidsystem, appropriate ow controls can be interposed in the piping to theheat exchanger and electrical controls positioned in or on the chillerto provide any desired predetermined temperature. It will be appreciatedthat there are many ways to control the operation of a heat exchangedevice such as device 65 by control devices for controlling the fluidflow in response to the temperature of the Water or the like that is inthe chiller.

The foregoing description and the drawings are given merely to explainand illustrate my invention and the manner in which it may be performed,and the invention is not to be limited thereto except in so far as theappended claims are so limited since those skilled in the art who havemy disclosure before them will be able to make modifications andvariations therein without departing from the scope of the invention.

I claim.:

l. In apparatus of the class described, the combination of a chillertank through which a liquid is adapted to be circulated, a refrigeratingsystem adapted to cool said liquid including a compressor, a condenser,and an evaporator connected in series in a closed loop with avaporizable refrigerant therein and with the evaporator being located insaid chiller tank, and heating means for maintaining the temperature ofthe evaporator suiciently above that of the condenser when the system isshut down and the apparatus is completely out of use for long periods oftime whereby condensation of refrigerant does not take place in theevaporator while the system is shut down. 1

2. In apparatus of the class described, the combination of a chillertank through which a liquid is adapted to be circulated, a refrigeratingsystem adapted to cool said liquid including a compressor, a condenser,and an evaporator connected in series in a closed loop with avaporizable refrigerant therein and with the evaporator located in saidchiller tank, a source of electrical power for operating saidcompressor, electrical controls for controlling said system in responseto demand, said controls being selectively connectible to said source ofelectrical power, and heating means for maintaining the temperature ofsaid evaporator above that of said condenser when the system is shutdown, said power is disconnected from said compressor and controls, andthe apparatuspis completely outof use for long periods of time.

3. Apparatus as set forth in claim 2 in which said heating meansincludes a heating device mounted in the chller tank and constructed andarranged to supply heat to said evaporator at a rate that will besuicient merely to maintain at all times the temperature of saidevaporator above that of the condenser.

4. Apparatus as set forth in claim 1 in which said heating meanscomprises a continuously operating low wattage electrical heater havingheat exchange relationship with the liquid in the cooler.

References Cited in the le of this patent UNITED STATES PATENTS HassellFeb. 7, 1933 Tidd Mar. 27, 1934 Yoder Nov. 24, 1936 Potter Nov. 12, 1940Smith June 13, 1950 Lee May 20, 1952 Kohlstedt Aug. 25, 1953 Raney Aug.31, 1954 Sardeson Sept. 28, 1954 Binder Apr. 12, 1955

